Component Testing Test Setup TapLok Insert Shear Key Copper Threads Friction Tests Collar Shear Tests NSTX TF FLAG JOINT REVIEW 8/7/03 Michael Kalish

TapLok Threaded Inserts A “TapLok” 3/8-16 “Medium Length” insert is used (OD into copper is.50” (OD =.562”, length =.562”)) Loading: –The stud preload of 5,000 lbf results in 11,800 psi (10,069 psi) in shear at the outer threads of the insert into the copper. –Thermal + Mechanical loading adds a cyclic load of 1,800 psi Per the inspection certification the Cu Tensile strength = 38 kpsi and Yield strength = 36 kpsi. Material: C10700 Silver Bearing Copper, Hard Drawn (50% Cold Worked) Values of 34 kpsi used for yield to account for observation of slight degradation to hardness after thermal cycling

Cyclic Testing, TapLok Using same test setup medium length (.562”)Tap Lok inserts were cycled then pulled Test sample was heated to 100 C during cycling Six test pieces were cycled at 5,000 to 6,000 lbf for 50,000 cycles or greater –Test levels reflect the 1,000 cycle thermal loading case –Cycled with 1 Hz Sine Wave Two samples were cycled at 5,000 to 7,360 lbf to test at the 2x Stress at design life condition After cycling static pull tests determined if pull out strength had degraded

Un-Cycled SampleBreak Force TLC TLC TLC TLC TLC Average =12700 TapLok Static Pull Test Results Average pullout force for.562” TapLok was 12,700 lbf corresponding to a calculated ultimate shear stress of 29.9 KPSI (25.6 KPSI) This value derived from the test data is 36% (17%) higher than the assumed ultimate strength in the fatigue analysis and twice the design load

Results Cyclic Pull Tests for TapLok No Failure of any sample including two samples cycled at 2x Stress and 50,000 cycles (5,000 lbf to 7,360 lbf) Pull out strength relatively unchanged for samples cycled at design loads Yield strength values averaged 82% of Tensile strength Samples cycled at temperature did not vary from unheated samples

Flag Stud Loading & Stress Summary With the 5,000 lbf preload and the thermal loading applied the stud sees a max stress of 74.7 ksi The ultimate tensile strength for the Inconel 718 stud is 210 ksi and the yield strength is 185 ksi Stud Nominal Loading Stud Nominal Loading + Thermal Axial Preload lbf5000 Cyclical Axial Loading lbf Maximum Axial Load Stud Preload Stress64935 Stud Cyclical VonMises Stress Stud Static Factor of Safety VonMises

Fasteners / Joint Design Michael Kalish NSTX TF FLAG JOINT REVIEW 8/7/03

Modified Goodman Diagram for Insert in Copper Conductor

Flag Stud Loading A preload of 5,000 lbf is applied with an equivalent stress of 64,900 psi Thermal loading after ratcheting of the flag temperature applies an enforced deflection of.0043 inches Thermal ratcheting +mechanical loading adds 9,800 psi

Modified Goodman Diagram For Stud

Stud Preload Maintaining the preload on the stud is critical for maintaining contact pressure and contact resistance Using a long narrow stud results in a much higher stud elasticity relative to the flag Stud elasticity keeps fatigue loading for the stud and insert low relative to the applied loading

Minimum Contact Pressure in 5.00 in Width - W =.79 in; Bolt Hole Dia. =.406 in Contact Area - A C =.79 in x 5.00 in – 4 (π x (.406 in) 2 )/ 4 = in 2 Bolt Pretension Force – F PRE = 4 x 5000 lbf = lbf Minimum Force - F MIN = 4 x 3300 lbf = 13,200 lbf Pretension Contact Pressure – P PRE = F PRE / A C = 5843 psi Minimum Contact Pressure - P MIN = F MIN / A C = 3846 psi (without Belleville washers)

Leverage Previous Design Experience Flag Material: C10700 H002, Silver Bearing Copper, Half Hard. Keep copper thread shear stress below 11,800 psi to eliminate need for retesting. Tap-lok inserts: Use longest insert possible for given size. Stud Material: Inconel 718. Pretension much less than.75 yield strength (copper thread shear stress dominates). Use Belleville washers and/ or Direct Tension Indicating (DTI) washers to monitor bolt pretension, reduce cyclic stress amplitude, and maintain bolt tension with thermal cycling and creep. Bolts loaded in tension only: separate shear load and compression load functions (rely on friction or separate feature to take shear load). Monitor joint electrical contact resistance.

NSTX Update Design Tap-Lok Inserts

NSTX Update Design Tap-Lok Inserts